Organic el display

ABSTRACT

An organic EL display device comprises a supporting substrate; and an organic EL element comprising an organic luminescent medium sandwiched between a lower electrode and an upper electrode thereon. A color changing medium and/or a transparent resin layer are arranged between the supporting substrate and the lower electrode. EL emission is taken out from the lower electrode. Any one of following expressions (5) to (8) is satisfied  
     n5≦n6≦n8  (5)  
     n5≦n7≦n8  (6)  
     n5≦n6≦n7≦n8  (7)  
     n5≦n7≦n6≦n8  (8)  
     wherein n5 represents a refractive index of the lower electrode, n6 represents a refractive index of the color changing medium, n7 represents a refractive index of the transparent resin layer, and n8 represents a refractive index of the supporting substrate. In such arrangement, a large quantity of EL emission can be taken to the outside.

TECHNICAL FIELD

[0001] The present invention relates to an organic EL display device,particularly an organic EL display device wherein the quantity of ELemission that can be taken out is large.

[0002] The “EL” described in claims and so on in the present descriptionis an abbreviated representation of “electroluminescence”.

BACKGROUND ART

[0003] Hitherto, attention has been paid to the utilization of ELdisplays using electroluminescence as luminescent elements in variousdisplay devices since the EL display devices have characteristics thatthe EL elements are capable of emitting light for itself, the capabilityof being watched and perceived is high, and they are superior inimpact-resistance because of the perfect solid state thereof.Particularly, organic EL display devices using an organic compound astheir luminescent material have been positively made practicable sincethe devices make it possible to lower voltage to be applied largely andcan easily be made thin and small-sized so that the consumption powerthereof can be made small.

[0004] Such an organic EL display device 100 is disclosed inJP-Laid/Open-Hei-10-289784 and JP-Laid/Open-Hei-11-185955. The outlineof this device 100 is illustrated in FIG. 6. An organic EL element 130is composed to sandwich an organic compound containing a luminescentlayer 124 between a lower electrode (conductive layer) 122 deposited ona supporting substrate 121 and an upper electrode (hole injectionelectrode) 125, and a sealing member 126 for excluding the effect ofmoisture in the atmosphere is set above this organic EL element 130.Furthermore, a color filter layer 127 is disposed on the face, oppositeto the organic EL element 130, of the sealing element 126. In theexample of this organic EL element 130, a nonconductive layer 123 isarranged between the lower electrode 122 and the luminescent layer 124.A void (for example, gas such as nitrogen) layer 131 is present betweenthe color filter layer 127 and the upper electrode 125.

[0005] Accordingly, by applying a given voltage between the upper andlower electrodes 122 and 125, EL emission passes from the side of theupper electrode 125, which is a transparent electrode, through the voidlayer 131, the color filter layer 127 and the sealing member 126 andthen the EL emission can be taken out. In FIG. 6, an arrow representsthe direction in which the EL emission is taken out.

[0006] As illustrated in FIG. 7, JP-Laid/Open-Hei-10-162958 discloses anorganic EL display device 200 wherein color changing layers 201 and 202,a protective layer 203, a transparent electrode 204, an organicluminescent layer 205 and a rear electrode 220 are disposed below aninsulating substrate (glass substrate) 210. The device 200 is composedso as to take out EL emission through the color changing layers 201 and202 from the side of the transparent electrode 204.

[0007] Therefore, by applying a given voltage between the upper and thelower electrodes 204 and 220, EL emission passes from the side of thetransparent electrode 204 through the protective layer 203, the colorchanging layers 201 and 202, and the insulating substrate 210 and thenthe EL emission can be taken out. In FIG. 7, an arrow represents thedirection in which the EL emission is taken out.

[0008] In the case that light passes through an interface between twolayers a and b made of constituent materials having different refractiveindexes, the relationship between the reflectivity R of the interface(the reflectivity against light perpendicular to the interface) and therefractive indexes n_(a) and n_(b) of the constituent materials of thetwo layers is represented by the following:

R=(n _(a) −n _(b))²/(n _(a) +n _(b))²

[0009] As can be understood from this expression, therefore, thereflectivity R of the interface becomes larger as the difference betweenthe refractive indexes n_(a) and n_(b) of the constituent materials ofthe two layers becomes larger. As a result, the quantity of the lighttransmitting through the interface decreases.

[0010] For example, when light is radiated from an indium zinc oxide(IZO, refractive index: 2.1) and the light comes through a void layer(refractive index: 1.0) into a glass substrate (refractive index: 1.5),the light quantity incoming in the glass substrate is reduced to 84% ofthe light quantity (100%) outgoing from the IZO on the assumption thatthe light absorbance of the respective layers themselves are zero.

[0011] However, according to the organic EL display devices disclosed inJP-Laid/Open-Hei-10-289784 and 11-185955, as the transparent conductivematerial constituting the upper electrode, an indium tin oxide (ITO)having a refractive index of about 2 or the like material is used, andthe refractive index of the void (gas such as nitrogen) layer betweenthe upper electrode and the sealing member is 1. Therefore, therefractive index difference between the upper electrode and the voidlayer and the refractive index difference between the void layer and thesealing member become large. In general, the color changing layers arealso made of a polymer material having a far larger refractive indexvalue than that of the void layer. For this reason, the refractive indexdifference between the void layer and the color changing layers alsobecomes large. This results in a problem that EL emission reflects onthe respective interfaces so that the quantity of the EL emission whichcan be taken out becomes remarkably small.

[0012] In the organic EL display device disclosed inJP-Laid/Open-Hei-10-162958, the relationship between the refractiveindexes of the respective layers is not considered. Therefore, ELemission reflects on the respective interfaces. The number of the layersthrough the EL emission must transmit is large. These facts result in aproblem that the quantity of the EL emission which can be taken out getsless.

[0013] JP-Laid/Open-Hei-7-272857 discloses an inorganic EL elementformed on a supporting substrate and having a structure wherein, on itsupper electrode side, a silicone oil (sealing agent) having a refractiveindex (s2) smaller than the refractive index (s1) of the upper electrodeand a protective layer having a refractive index (s3) smaller than thatof this silicone oil and larger than 1 are disposed and further ELemission is taken out from the side of the upper electrode.

[0014] However, when the silicone oil used in this inorganic EL elementis used as a sealing agent of an organic EL element, the silicone oilmay cause an organic luminescent medium in the organic EL element to bedissolved and invades into its layer interface to disturb its layerstructure. Thus, the organic EL element may be deteriorated and thedurability thereof may also be deteriorated.

[0015] In such an inorganic EL element, the luminescent brightnessthereof is originally low. Thus, even if each of the refractive indexesof its upper electrode, sealing agent and protective layer isconsidered, it is practically difficult that the inorganic EL elementexhibits performance equivalent to that of organic EL elements or iseasily produced.

[0016] Thus, the inventors of the present invention have found out thatby considering the relationship between the refractive indexes of asealing member and a color changing medium and those of a transparentelectrode and so on, the quantity of EL emission which can be taken outin an organic EL display device can be made large.

[0017] That is, an object is to provide an organic EL display devicewherein even if a sealing member is set up and EL emission is taken outthrough the sealing member in a first invention, even if a colorchanging medium is set up and EL emission is taken out through the colorchanging medium in a second invention, or even if a color changingmedium is arranged outside a supporting substrate and EL emission istaken out through the color changing medium in a third invention,reflection on each of interfaces is effectively suppressed so that thequantity of the EL emission which can be taken out is large.

DISCLOSURE OF THE INVENTION

[0018] According to the present invention (first invention), there isprovided an organic EL display device (which may be referred to as afirst organic EL display device) comprising; a supporting substrate; anorganic EL element comprising an organic luminescent medium sandwichedbetween a lower electrode and an upper electrode on the supportingsubstrate; a sealing medium; and a sealing member; EL emission beingtaken out from the upper electrode; wherein a following expression (1)is satisfied

n1≦n2≦n3  (1)

[0019] wherein n1 represents a refractive index of the upper electrode,n2 represents a refractive index of the sealing medium, and n3represents a refractive index of the sealing member.

[0020] It is sufficient for the present invention that the expressionsabout the refractive indexes described above are satisfied by at leastthe peak wavelength of EL emission or conversion light.

[0021] That is, such a structure makes it possible that even if thesealing member is provided and EL emission is taken out through thesealing member, reflection on each interface is suppressed so as toprovide an organic EL display device having a large luminescencequantity.

[0022] In the first organic EL display device, it is preferred that thedevice further comprises a color filter and/or a fluorescent medium,that is, a color changing medium (which may be referred to as a firstcolor changing medium) between the sealing medium and the sealingmember; and a following expression (2) is satisfied

n1≦n2≦n4≦n3  (2)

[0023] wherein n4 represents a refractive index of the color changingmedium.

[0024] Such a structure makes it possible that even if the sealingmember is provided and further the first color changing medium isprovided to display an image, reflection on each interface is suppressedso as to provide an organic EL display device having a largeluminescence quantity.

[0025] In the first organic EL display device, it is preferred that thedevice further comprises a color changing medium (which may be referredto as a second color changing medium) on a surface of the sealingmember, the surface opposite to a surface on which the sealing medium isarranged; and a following expression (3) is satisfied

[0026] n1≦n2≦n3≦n4′  (3)

[0027] wherein n4′ represents a refractive index of the color changingmedium.

[0028] Such a structure makes it possible that even if the sealingmember is provided and further the second color changing medium isprovided to display an image, reflection on each interface is suppressedso as to provide an organic EL display device having a largeluminescence quantity. Since the second color changing medium does notcontact the sealing medium directly, the second color changing mediummay not be deteriorated by the sealing medium. Moreover, it is possibleto prevent the generation of snapping or the like resulting fromirregularities on the surface of the second color changing medium.

[0029] In the first organic EL display device is formed, it is preferredthat the refractive indexes n1 and n2 satisfy a following expression(4):

n2≦=0.7×n1  (4)

[0030] Such a structure makes it possible to provide an organic ELdisplay device having a larger luminescence quantity since therefractive index n1 of the upper electrode and the refractive index n2of the sealing medium become nearer to each other.

[0031] In the first organic EL display device, it is preferred that therefractive index of the sealing medium is 1.56 or more.

[0032] Such a structure reduces danger of deterioration of the organicEL display device by the sealing medium and allows the selection ofmaterials of the upper electrode and the sealing member among a widerrange of various materials. A typical example of a sealing liquid havinga refractive index of less than 1.56 is silicone oil. In the case thatsuch silicone oil is used, this sealing liquid causes deterioration ofthe organic luminescent medium so that the durability thereof maydecrease.

[0033] In the first organic EL display device, it is preferred that thesealing medium comprises a transparent resin and/or a sealing liquid.

[0034] Such a structure makes it possible to prevent display defectsbased on light scattering since the sealing medium can be handled withless influence by taking-in of bubbles and so on.

[0035] In the first organic EL display device, it is preferred that thesealing medium comprises a transparent inorganic material.

[0036] Such a structure makes it possible to improve the reliability ofthe organic EL display device without hindering luminescence of theorganic EL and without oxidizing or deteriorating the organic EL elementreadily since the transparent inorganic material does not comprise watercontent, oxygen or low molecular monomers and has the higher blockingeffect.

[0037] The wording “comprises a transparent inorganic material” includesthe meaning of a transparent inorganic film or the material dispersed inthe above-mentioned transparent resin or sealing liquid.

[0038] In the first organic EL display device, it is preferred that theupper electrode is made mainly of an indium zinc oxide.

[0039] The use of the indium zinc oxide in the upper electrode makes itpossible to satisfy the above-mentioned expression (1) or (2) since therefractive index of the indium zinc oxide is as high as about 2.1.

[0040] According to another aspect (second invention) of the presentinvention, there is provided an organic EL display device (which may bereferred to a second organic EL display device) comprising; a supportingsubstrate; and an organic EL element comprising an organic luminescentmedium sandwiched between a lower electrode and an upper electrode, onthe supporting substrate; a color changing medium (which may be referredto as a third color changing medium) and/or a transparent resin layerbeing arranged between the supporting substrate and the lower electrode;EL emission being taken out from the lower electrode; wherein any one offollowing expressions (5) to (8) is satisfied

n5≦n6≦n8  (5)

n5≦n7≦n8  (6)

n5≦n6≦n7≦n8  (7)

n5≦n7≦=n6≦n8  (8)

[0041] wherein n5 represents a refractive index of the lower electrode,n6 represents a refractive index of the color changing medium, n7represents a refractive index of the transparent resin layer, and n8represents a refractive index of the supporting substrate.

[0042] Such a structure makes it possible that even if the third colorchanging medium and the transparent resin layer are provided and ELemission is taken out from the lower electrode, reflection on eachinterface is suppressed so as to provide an organic EL display devicehaving a large luminescence quantity.

[0043] The third color changing medium may be of monolayer structurecomposed of either of a color filter or a fluorescent medium, may be ofmultilayer structure wherein color filters and/or fluorescent mediumsare laminated.

[0044] In the case that the color changing medium is of multilayerstructure, in the above-mentioned expression (5), the refractive indexn6 of the color changing medium is defined as follows.

[0045] That is, when the third color changing medium is of m-layerstructure and the refractive indexes of the layers are represented byn6(1), n6(2), . . . and, n6(m) from the lower electrode side, theexpression (5) is defined as being satisfied by satisfying theexpression (5)′:

n5≦n6(1)≦n6(2)≦ . . . >n6(m)≦n8  (5)′

[0046] Therefore, for example, when the third color changing medium isof two-layer structure and further the refractive indexes of the twolayers are represented by n6(1) and n6(2) from the lower electrode side,the expression (5) is defined as being satisfied by satisfying theexpression (5)″:

n5≦n6(1)≦n6(2)≦n8  (5)″

[0047] The above-mentioned definition can be applied to not only theabove-mentioned expressions (7) and (8), but also a refractive index ofanother layer constituting the organic EL display device.

[0048] According to a further aspect (third invention) of the presentinvention, there is provided an organic EL display device (which may bereferred to a third organic EL display device) comprising; a supportingsubstrate; and an organic EL element comprising an organic luminescentmedium sandwiched between a lower electrode and an upper electrode, onthe supporting substrate; a color changing medium (which may be referredto as a fourth color changing medium) being arranged on a surface of thesupporting substrate, the surface opposite to a surface on which thelower electrode is arranged; EL emission being taken out from the sideof the lower electrode; wherein a following expression (9) is satisfied

n5≦=n8≦=n9  (9)

[0049] wherein n5 represents a refractive index of the lower electrode,n8 represents a refractive index of the supporting substrate, and n9represents a refractive index of the color changing medium.

[0050] Such a structure makes it possible that even if EL emission istaken out through the fourth color changing medium from the lowerelectrode side, reflection on each interface is suppressed so as toprovide an organic EL display device having a large luminescencequantity.

[0051] In the third organic EL display device, it is preferred that atransparent resin layer is arranged between the lower electrode and thesupporting substrate, and a following expression (10) is satisfied;

n5≦n7≦n8≦n9  (10)

[0052] wherein n7 represents a refractive index of the transparent resinlayer.

[0053] Such a structure makes it possible that even if the fourth colorchanging medium and the transparent resin layer are provided to take outEL emission from the lower electrode side, reflection on each interfaceis suppressed so as to provide an organic EL display device having alarge luminescence quantity.

[0054] In the third organic EL display device, it is preferred that therefractive index n5, and the refractive index n6 or n7 satisfy thefollowing expression (11) or (12).

n6≦0.7×n5  (11)

n7≦0.7×n5  (12)

[0055] Such a structure makes it possible to provide an organic ELdisplay device having a larger luminescence quantity since therefractive index n5 of the lower electrode becomes nearer to therefractive index n6 of the third color changing medium or the refractiveindex n7 of the transparent resin layer.

[0056] In the first, second or third organic EL display device, it ispreferred that a thin film transistor (hereinafter referred to as a TFT)for driving the organic EL element is arranged on the supportingsubstrate.

[0057] Such a structure allows significantly low driving voltage withenhanced luminescence efficiency and lower power consumption.

BRIEF DESCRIPTION OF DRAWINGS

[0058]FIG. 1 is a graph showing relationship between the refractiveindex of a sealing medium and the transmittance thereof.

[0059]FIG. 2 is a sectional view of an organic EL display device in afirst embodiment.

[0060]FIG. 3 is a sectional view of an organic EL display device in asecond embodiment.

[0061]FIG. 4 is a circuit diagram of one example of active driving typeorganic EL display devices.

[0062]FIG. 5 is a perspective view in a plane direction of the activedriving type organic EL display device according to the circuit diagramillustrated in FIG. 4.

[0063]FIG. 6 is a sectional view of a conventional organic EL displaydevice (No. 1).

[0064]FIG. 7 is a sectional view of a conventional organic EL displaydevice (No. 2).

BEST MODE FOR CARRYING OUT THE INVENTION

[0065] Embodiments of the present invention will be specificallydescribed with reference to the drawings. In the drawings which arereferred to, the size of respective constituent components, the shapethereof and the arrangement relationship therebetween are roughlyillustrated in such a manner that this invention can be merelyunderstood. Therefore, this invention is not limited to illustratedexamples. In the drawings, hatching, which represents sections, may beomitted.

[0066] [First Embodiment]

[0067] As illustrated in FIG. 2, the first embodiment is specifically anactive matrix type organic EL display device 62 wherein TFTs 14 embeddedin an electrically insulator (including a gate insulating film) 12, aninter-insulator (flattening film) 13, organic EL elements 26 and contactholes (electrically connecting members) 48 for connecting the TFTs 14and the organic EL elements 26 electrically are disposed on a supportingsubstrate (which may be referred to only as a substrate) 10. The device62 further comprises a sealing medium 16, a color changing medium 60 anda sealing member 58.

[0068] The refractive index of an upper electrode 20 in the organic ELelement 26, that of the sealing medium 16 and that of the sealing member58 are represented by n1, n2 and n3, respectively. In this case, thefollowing expression (1) is satisfied in the active matrix type organicEL display device 62.

n1≦n2≦n3  (1)

[0069] The following will describe the constituent elements and so on inthe first embodiment, referring to FIG. 2 and so on.

[0070] 1. Refractive Index {circle over (1)} Expression (1)

[0071] In the organic EL display device of the first embodiment, therefractive indexes of the respective layers satisfy at least theexpression (1), as described above.

[0072] That is, by satisfying the expression (1) in this way, thereflectance of EL on interfaces between the respective layers can bereduced so that an organic EL display device having a large luminescencequantity can be provided.

[0073] For example, when light is radiated from the upper electrode madeof an indium zinc oxide (IZO, refractive index: 2.1) and the light comesthrough the sealing medium (refractive index: 1.7) into the sealingmember (refractive index: 1.5), the quantity of the light which can comein the sealing member becomes a high value, such as 98.6% of thequantity (100%) of the light outgoing from the upper electrode on theassumption that the light absorbance of the respective layers themselvesare 0%. In other words, it can be understood that light hardly reflectson the respective interfaces.

[0074] Assuming, as a model, a case in which light is radiated outsidefrom the side of the upper electrode (IZO, refractive index: 2.1) andthen the light comes through the sealing medium into the sealing member(refractive index: 1.5) in the organic EL element made illustrated inFIG. 2, the relationship between the refractive index of the sealingmedium and the quantity of the light incoming in the sealing member canbe shown as in FIG. 1. Namely, in FIG. 1, its transverse axis representsthe refractive index value of the sealing medium and its vertical axisrepresents the transmittance (%) of the sealing medium, that is, thepercentage of the quantity of the light incoming in the sealing member.For example, when this transmittance is 100(%), it is meant that all ELemission taken out from the organic EL element comes in the sealingmember without being absorbed in the sealing medium or reflectedthereon.

[0075] As can be understood from FIG. 1, when the expression (1) issatisfied and the refractive index of the sealing medium becomes nearerto the refractive index value of the upper electrode, the percentage ofthe quantity of the light incoming in the sealing medium trends to belarger.

[0076] In this example, therefore, a high transmittance of 97% or morecan be obtained in the sealing medium by satisfying the expression (1).

[0077] The refractive index is defined as a refractive index relative to1 as the value of vacuum. If interfaces between the respective layers ofthe upper electrode, the sealing medium and the sealing member are mixedwith each other to be indefinite, the mixed layer is defined as anaverage refractive index. However, even if the mixed layer is present,it is preferred that the average refractive index becomes smallersuccessively from the upper electrode to the sealing member. {circleover (2)} Expression (2)

[0078] As illustrated in FIG. 2, when the first color changing medium 60is arranged between the sealing medium 16 and the sealing member 58 andfurther the refractive index of the first color changing medium 60 isrepresented as n4 in the organic EL display device 62 of the firstembodiment, it is more preferred to satisfy the above-mentionedexpression (1) and further satisfy the following expression (2).

n1≦n2≦n4≦n3  (2)

[0079] When in such a structure, light is radiated from the upperelectrode made of, for example, an indium zinc oxide (IZO, refractiveindex: 2.1) and then the light comes through the sealing medium(refractive index: 1.6) and the first color changing medium (refractiveindex: 1.55) into the sealing member (refractive index: 1.5), thequantity of the light which can come in the sealing member becomes ahigh value of 98% of the light quantity (100%) outgoing from the upperelectrode on the assumption that the light absorbance of the respectivelayers themselves are 0%. {circle over (3)} Expression (3)

[0080] When the second changing medium is disposed on the side, oppositeto the sealing medium, of the sealing member, that is, the side whichcontacts the air and further the refractive index of the second colorchanging medium represented as n4′ in the organic EL display device ofthe first embodiment, it is more preferred to satisfy theabove-mentioned expression (1) and further satisfy the followingexpression (3).

n1≦n2≦n3≦n4′  (3)

[0081] When in such a structure, light is radiated from the upperelectrode made of, for example, an indium zinc oxide (IZO, refractiveindex: 2.1) and then the light comes through the sealing medium(refractive index: 1.7) and the sealing member (refractive index: 1.55)into the second color changing medium (refractive index: 1.5), thequantity of the light which can come in the second color changing mediumbecomes a high value of 99% of the light quantity (100%) outgoing fromthe upper electrode on the assumption that the light absorbance of therespective layers themselves are 0%. {circle over (4)} Expression (4)

[0082] In the organic EL display device of the first embodiment, it ispreferred that the refractive index n1 of the upper electrode and therefractive index n2 of the sealing medium satisfy the above-mentionedexpression (1) and further satisfy the following expression (4).

n2≦0.7×n1  (4)

[0083] When in such a structure, light is radiated from the upperelectrode made of, for example, an indium zinc oxide (IZO, refractiveindex: 2.1) and then the light comes through the sealing medium(refractive index: 1.55) into the sealing member (refractive index:1.5), the quantity of the light which can come in the sealing mediumbecomes a high value of 98% of the light quantity (100%) outgoing fromthe upper electrode on the assumption that the light absorbance of therespective layers themselves are 0%.

[0084] 2. Substrate

[0085] (1) Kind

[0086] The substrate (which may be referred to as the supportingsubstrate) in the organic EL display device is a member for supportingthe organic EL elements, TFTs and so on. It is therefore preferred thatthe mechanical strength and the dimensional stability thereof aresuperior.

[0087] Examples of such a substrate are substrates made of an inorganicmaterial, such as a glass plate, a metal plate, and a ceramic plate.Preferred examples of the inorganic material include glass material,silicon oxide, aluminum oxide, titanium oxide, yttrium oxide, germaniumoxide, zinc oxide, magnesium oxide, calcium oxide, strontium oxide,barium oxide, lead oxide, sodium oxide, zirconium oxide, sodium oxide,lithium oxide, boron oxide, silicon nitride, soda lime glass,barium/strontium-containing glass, lead glass, aluminosilicate glass,borosilicate glass, and barium borosilicate glass.

[0088] Preferred examples of an organic material constituting thesubstrate include polycarbonate resin, acrylic resin, vinyl chlorideresin, polyethylene terephthalate resin, polyimide resin, polyesterresin, epoxy resin, phenol resin, silicone resin, fluorine resin,polyvinyl alcohol resin, polyvinyl pyrrolidone resin, polyurethaneresin, epoxy resin, cyanate resin, melamine resin, maleic resin, vinylacetate resin, polyacetal resin and cellulose resin.

[0089] (2) Surface Treatment, and so on

[0090] In order to avoid the invasion of moisture into the organic ELdisplay device, it is also preferred that the substrate made of any oneof these materials is subjected to moisture-proof treatment orhydrophobic treatment by forming an inorganic film or applying fluorineresin.

[0091] This is particularly effective when an organic material such as apolymer is used.

[0092] In order to avoid the invasion of moisture into the organicluminescent medium, it is preferred to make the water content in thesubstrate and the gas permeability coefficient thereof small.Specifically, it is preferred that the water content in the supportingsubstrate is 0.0001% by weight or less and the gas permeabilitycoefficient is 1×10⁻¹³ cc·cm/cm²·sec.cmHg or less.

[0093] In order to take out EL emission from the side of the upperelectrode in the first embodiment, it is unnecessary that the substrateitself has transparency. However, in the case that EL emission is takenout through the substrate (also in the case of use as the sealingmember), it is preferred to use, among the above-mentioned substratematerials, the substrate material having a light transmittance of 70% ormore particularly at a wavelength of 400 to 700 nm.

[0094] (3) Refractive Index

[0095] It is preferred to set the refractive index of the substrate inthe range of 1.4 to 1.8. This is because by setting the refractive indexwithin such a range the constituent material of the substrate which canbe used can be selected from wider range of materials.

[0096] This is also because by setting the refractive index of thesubstrate in such a range, the above-mentioned expressions can besatisfied in the relationships to the refractive index of the upperelectrode and that of the lower electrode.

[0097] Furthermore, this is because such a substrate makes it possibleto suppress reflection on the surface of the substrate, even if ELemission is taken out through the substrate.

[0098] For reference, the values of the refractive indexes of preferredsubstrates are as follows: methyl methacrylate resin 1.49 silicon oxide(SiO₂) 1.54 boron oxide (B₂O₃) 1.77 glass 1.49-1.50 tetrafluoroethyleneresin 1.49

[0099]3. Organic EL Element

[0100] (1) Organic Luminescent Medium

[0101] The organic luminescent medium can be defined as a mediumcontaining an organic luminescent layer wherein an electron and a holeare recombined with each other so that EL can be emitted. This organicluminescent medium can be made, for example, by depositing the followinglayers on an anode:

[0102] {circle over (1)} organic luminescent layer

[0103] {circle over (2)} hole injection layer/organic luminescent layer

[0104] {circle over (3)} organic luminescent layer/electron injectionlayer

[0105] {circle over (4)} hole injection layer/organic luminescentlayer/electron injection layer

[0106] {circle over (5)} organic semiconductor layer/organic luminescentlayer

[0107] {circle over (6)} organic semiconductor layer/electron barrierlayer/organic luminescent layer

[0108] {circle over (7)} hole injection layer/organic luminescentlayer/adhesion improving layer

[0109] Among these, the structure {circle over (4)} is preferably usedsince it can give a higher luminescent brightness and is also superiorin durability.

[0110] {circle over (1)} Constituent Material

[0111] Examples of the luminescent material in the organic luminescentmedium include one or a combination of two or more selected fromp-quaterphenyl derivatives, p-quinquphenyl derivatives, benzothiazolecompounds, benzoimidazole compounds, benzoxazole compounds,metal-chelated oxinoid compounds, oxadiazole compounds, styrylbenzenecompounds, distyrylpyrazine derivatives, butadiene compounds,naphthalimide compounds, perylene derivatives, aldazine derivatives,pyrazine derivatives, cyclopentadiene derivatives, pyrrolopyrrolederivatives, styrylamine derivatives, coumarin compounds, aromaticdimethylidyne compounds, metal complexes having a ligand of a8-quinolynol derivative, and polyphenyl compounds.

[0112] Among these organic luminescent materials,4,4′-bis(2,2-di-t-butylphenylvinyl)biphenyl (abbreviated to DTBPBBi) and4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviated to DPVBi) as aromaticdimethylidyne compounds, and derivatives thereof are more preferred.

[0113] Furthermore, it is preferred to use a material wherein an organicluminescent material having a distyrylarylene skeleton or the like, as ahost material, is doped with a fluorescent dye giving intense blue andred fluorescence, for example, a coumarin material, or a fluorescent dyesimilar to the host, as a dopant. More specifically, it is preferred touse the above-mentioned DPVBi or the like as a host and useN,N-diphenylaminobenzene (abbreviated to DPAVB) as a dopant.

[0114] It is also preferred to use a high molecular material (numberaverage molecular weight: 10000 or more) as well as the above-mentionedlow molecular material (number average molecular weight: less than10000).

[0115] Specific examples thereof include polyarylene vinylene,derivatives thereof (PPV), polyfluorene, derivatives thereof, andfluorene-containing copolymers.

[0116] {circle over (2)} Thickness

[0117] The thickness of the organic luminescent medium is notparticularly limited. It is however preferred to arrange the thicknessin the range of, for example, 5 nm to 5 μm.

[0118] The reasons for this are as follows: if the thickness of theorganic luminescent medium is below 5 nm, the luminescent brightness anddurability thereof may deteriorate, and if the thickness of the organicluminescent medium is over 5 μm, the value of the voltage to be appliedmay become high.

[0119] Therefore, the thickness of the organic luminescent medium ismore preferably in the range of 10 nm to 3 μm, and is still morepreferably in the range of 20 nm to 1 μm.

[0120] (2) Electrodes

[0121] The following will describe an anode layer and a cathode layer asthe electrodes. The anode layer and the cathode layers become the upperand the lower electrodes, respectively, or the lower and upperelectrodes, respectively, dependently on the structure of the organic ELelement.

[0122] {circle over (1)} Anode Layer

[0123] It is preferred to use, for the anode layer, a metal, an alloy oran electrically conductive compound having a large work function (forexample, 4.0 eV or more), or a mixture thereof. Specifically, it ispreferred to use one or a combination of two or more selected fromindium tin oxide (ITO), indium zinc oxide (IZO), indium copper (CuIn),tin oxide (SnO₂), zinc oxide (ZnO), gold, platinum, palladium and so on.

[0124] By using these electrode materials, the anode layer having auniform thickness can be made by a method making film-deposition in adry state possible, such as vacuum deposition, sputtering, ion plating,electron beam evaporation, CVD (chemical vapor deposition), MOCVD (metaloxide chemical vapor deposition), or plasma CVD.

[0125] In the case that EL emission is taken out from the side of theanode layer, it is necessary to make the anode layer to a transparentelectrode. On the other hand, in the case that EL emission is not takenout, it is unnecessary to make the anode electrode to a transparentelectrode. Therefore, in the case that the anode layer is made to atransparent electrode, it is preferred to use a transparent conductivematerial such as ITO, IZO, CuIn, SnO₂, or ZnO, and provide thetransmittance of EL emission to a value of 70% or more.

[0126] The film thickness of the anode layer is not particularlylimited. The thickness is preferably in the range of, for example, 10 to1,000 nm, and is more preferably in the range of 10 nm to 200 nm.

[0127] The reason for this is as follows: by setting the film thicknessof the anode layer in such a range, good electrically connectingreliability can be obtained between the anode layer and electricallyconnecting members made of IZO, and further such a film thickness makesit possible to obtain the transmittance of EL emission, for example, 70%or more.

[0128] In the case that EL emission is taken out from the side of theanode layer, it is preferred to set the refractive index of the anodelayer in the range of 1.6 to 2.2. This is because, by setting therefractive index in such a range, it is possible to satisfy theabove-mentioned expressions (1) and so on easily, and anode materialswhich can be used are selected from wider range of materials.

[0129] It is therefore more preferred to set the refractive index of theanode layer in the range of 1.7 to 2.1.

[0130] In order to make the adjustment of the relationships about therefractive indexes easy, it is more preferred to use an indium zincoxide (refractive index: 2.1) among the above-mentioned constituentmaterials of the anode layer.

[0131] {circle over (2)} Cathode Layer

[0132] It is preferred to use, for the cathode layer, a metal, an alloyor an electrically conductive compound having a small work function (forexample, less than 4.0 eV), a mixture thereof, or an inclusion thereof.

[0133] Specifically, it is preferred to use one or a combination of twoor more selected from sodium, sodium-potassium alloy, cesium, magnesium,lithium, magnesium-silver alloy, aluminum, aluminum oxide,aluminum-lithium alloy, indium, rare earth metals, mixtures of any oneof these metals and an organic luminescence medium material, mixtures ofany one of these metals and an electron injection layer material, and soon.

[0134] The film thickness of the cathode layer is not particularlylimited in the same way as in the anode layer. Specifically, thethickness is preferably in the range of 10 to 1,000 nm, and is morepreferably in the range of 10 nm to 200 nm.

[0135] The reason for this is as follows: by setting the film thicknessof the cathode layer in such a range, good electrically connectingreliability can be obtained between the cathode layer and electricallyconnecting members made of IZO, and further such a film thickness makesit possible to obtain the transmittance of EL emission, for example, 10%or more, more preferably 70% or more.

[0136] In the case that light is taken out from the side of the cathodelayer, it is preferred to set the refractive index of the cathode layerin the range of 1.6 to 2.2 in the same way as in the case of the anodelayer.

[0137] (3) Inter-Insulator

[0138] The interlayer dielectric in the organic EL display device of thepresent invention is present near or around the organic EL elements andthe TFTs, and causes the unevenness of a luminescent medium or a colorfilter to be flattened, so as to be used mainly as a flattened undercoatwhen the lower electrode of the organic EL element is formed. Theinterlayer dielectric is also used to attain electric insulation forforming high resolution wiring materials, electric insulation(prevention of short circuits) between the lower and upper electrodes ofthe organic EL element, electrical insulation or mechanical protectionof the TFT, electrical insulation between the TFT and the organic ELelement, and so on.

[0139] Therefore, the inter-insulator may be called a flattening film,an electrically insulating film, a partition, a spacer, or the like ifnecessary. The present invention embraces all of them.

[0140] {circle over (1)} Constituent Material

[0141] Examples of the constituent material used for the inter-insulatorusually include acrylic resin, polycarbonate resin, polyimide resin,fluorinated polyimide resin, benzoguanamine resin, melamine resin,cyclic polyolefin, Novolak resin, polyvinyl cinnamate, cyclic rubber,polyvinyl chloride resin, polystyrene, phenol resin, alkyd resin, epoxyresin, polyurethane resin, polyester resin, maleic acid resin, andpolyamide resin.

[0142] In the case that the inter-insulator is composed of an inorganicoxide, examples of preferred oxides include silicon oxide (SiO₂ orSiO_(x)), aluminum oxide (Al₂O₃ or AlO_(x)), titanium oxide (TiO₂),yttrium oxide (Y₂O₃ or YO_(x)), germanium oxide (GeO₂ or GeO_(x)), zincoxide (ZnO), magnesium oxide (MgO or MgO_(x)), calcium oxide (CaO),boric acid (B₂O₃), strontium oxide (SrO), barium oxide (BaO), lead oxide(PbO), zirconia (ZrO), sodium oxide (Na₂O), lithium oxide (Li₂O), andpotassium oxide (K₂O). The symbol x in the structural formulaerepresenting the inorganic oxides is in the range of 1 to 3.

[0143] In the case that heat-resistance is particularly required, it ispreferred to use acrylic resin, polyimide resin, fluorinated polyimide,cyclic polyolefin, epoxy resin, or any inorganic oxide among theseconstituent materials of the inter-insulator.

[0144] These inter-insulator can be worked into a desired pattern byintroducing a photosensitive group thereto and using photolithography,or can be formed into a desired pattern by printing.

[0145] {circle over (2)} Thickness of the Inter-Insulator, and so on

[0146] The thickness of the inter-insulator depends on the resolution ofdisplay, and the degree of the unevenness of a fluorescent medium or acolor filter combined with the organic EL element, and is preferably inthe range of 10 nm to 1 mm.

[0147] This is because such a structure makes it possible to make theunevenness of the fluorescent medium or the color filter sufficientlyflat or reduce the dependency of the high resolution display on viewingangle.

[0148] Accordingly, the thickness of the inter-insulator is morepreferably in the range of 100 nm to 100 μm, and is still morepreferably in the range of 100 nm to 10 μm.

[0149] 4. Sealing Member

[0150] {circle over (1)} Structure of the Sealing Member

[0151] In order to prevent moisture from invading the inside of theorganic luminescent medium 24, it is preferred that the sealing member58 illustrated in FIG. 2 is covered at least the luminescent area of theorganic EL display device 62.

[0152] As such a sealing member, the same material for the supportingsubstrate can be used. Particularly, a glass plate having a high effectof shielding moisture or oxygen can be used. The form of the sealingmember is not particularly limited, and is preferably, for example, aplate form or a cap form. For example, in the case of a plate form, thethickness thereof is preferably in the range of 0.01 to 5 mm.

[0153] It is also preferred that the sealing member is fitted into agroove or the like made in a part of the supporting substrate underpressure and is then fixed thereto, or that the sealing member is fixedto a part of the supporting member with a photo-setting adhesive agentor the like.

[0154] {circle over (2)} Sealing Medium

[0155] The sealing medium is preferably arranged between the sealingmember and the organic EL display device. Examples of such a sealingmedium include a transparent resin, a sealing liquid and a transparentinorganic material.

[0156] The refractive index of the sealing medium is preferably 1.5 ormore. The reason is as follows: since the sealing medium contacts thetransparent electrode (refractive index: about 1.6 to 2.1), therefractive index of the sealing medium can be made near to that of thetransparent electrode by setting the refractive index of the sealingmedium 1.5 or more. In this way, reflection of light on the interfacetherebetween can be suppressed.

[0157] Since reflection of light on the interface between thetransparent electrode and the sealing medium can be more suppressed andthe kind of the constituent material of the sealing medium is notexcessively restricted, the refractive index of the sealing medium ismore preferably 1.56 or more, and is still more preferably in the rangeof 1.58 to 2.0.

[0158] It is also preferred to use, as a main component, an aromaticring containing compound, a fluorine skeleton containing compound, abromine containing compound, or a sulfur containing compound in thetransparent resin or the sealing liquid constituting the sealing medium,or add the same, as a refractive index adjusting agent, thereto. This isbecause such a compound has a relatively high refractive index and makesit possible to adjust the refractive index flexibly if necessary.

[0159] Furthermore, in the case that the sealing medium is a transparentresin, the resin is preferably a ultraviolet ray setting resin, avisible ray setting resin, a thermosetting resin, or an adhesive agentusing such a resin. Specific examples thereof include Luxtrak LCR0278and 0242D (both of which are made by Toagosei Co., Ltd., TB3102 (epoxytype, made by Three Bond Co., Ltd.) and Venefix VL (acrylic type, madeby Adel Co., Ltd.), which are commercially available.

[0160] More preferred examples of the transparent resin constituting thesealing medium are as follows: polyphenyl methacrylate (refractiveindex: 1.57) polyethylene terephthalate (refractive index: 1.58)poly-o-chlorostyrene (refractive index: 1.61) poly-o-naphthylmethacrylate (refractive index: 1.61) polyvinyl naphthalene (refractiveindex: 1.68) polyvinyl carbazole (refractive index: 1.68) polyestercontaining fluorene skeleton (refractive index: 1.61 to 1.64)

[0161] It is also preferred to add alkoxy titanium such as dimethoxytitanium or diethoxy titanium in the transparent resin or the sealingliquid constituting the sealing medium.

[0162] The addition of the alkoxy titanium in this way makes it possibleto make the refractive index of the transparent resin or the sealingliquid to a higher value.

[0163] A transparent inorganic material is preferably contained as thesealing medium. Examples of the transparent inorganic material includeSiO₂, SiO_(x), SiO_(x)N_(y), Si₃N₄, Al₂O₃, AlO_(x)N_(y), TiO₂ andTiO_(x).

[0164] In the case of forming the transparent inorganic material film,the film is preferably formed at a low temperature (100° C. or lower)and a slow film-forming speed in order that the organic EL element isnot deteriorated. Specifically, a method such as sputtering, vapordeposition or CVD is preferred.

[0165] These transparent inorganic material films are preferably in anamorphous form since the amorphous films have a high effect of shieldingmoisture, oxygen, a low molecular monomer and so on and suppress thedeterioration of the organic EL element.

[0166] In the case of forming a layer wherein the transparent inorganicmaterial is dispersed, a solution wherein transparent inorganic materialparticles are dispersed in the transparent resin or the sealing liquidis prepared and this solution may be made into a film by spin coating,roll coating or casting. Alternatively, the inorganic material in aliquid form may be inject under the sealing member.

[0167] In the above-mentioned sealing medium, layers made of materialsof different kinds may be composed as plural layers.

[0168] In the case that the sealing medium is composed of plural layersbut the refractive indexes of the respective layers are indefinite, theaverage refractive index of the plural layers may be defined as therefractive index of the sealing medium. In this case, however, it isnecessary that the magnitude order of the upper electrode (n1), thesealing medium (n2) and the sealing member (n3) is as follows: n1≦n2≦n3

[0169] 5. Thin Film Transistor (TFT)

[0170] (1) Structure

[0171] One embodiment of the organic EL display device of the presentinvention has the plural TFTs 14 and the plural organic EL elements 26driven correspondingly to the TFTs 14 on the substrate 10, asillustrated in FIG. 2.

[0172] As illustrated in FIG. 2, the flattened inter-insulator 13 isarranged between the TFTs 14 and the lower electrodes 22 of the organicEL elements 26, and further the drain 47 of the TFT 14 and the lowerelectrode 22 of the organic EL element 26 are electrically connected toeach other through the contact hole 48 made in the inter-insulator 13.

[0173] A circuit diagram in one example of such an organic EL displaydevice is illustrated in FIG. 4. This circuit diagram illustrates thefollowing: gate lines (scanning electrode lines) and source lines(signal electrode lines) are formed on the substrate so as to be in anXY matrix form. About each pixel, the following are connected to thegate lines and the source lines: two TFTs 55 and 56 and a condenser 57for holding the gate of the second TFT 55 at a constant voltage. In thismanner, the organic EL element 62 can be driven by the second TFT 56.

[0174]FIG. 5 is a perspective view in a plane direction of the organicEL display device according to the circuit diagram illustrated in FIG.4.

[0175] Preferably, plural scanning electrode lines (Y_(j) to Y_(j+n)) 50and signal electrode lines (X_(i) to X_(1+n)) 51 arranged in an XYmatrix form are also electrically connected to the TFTs 55 and 56 so asto make electric switches for driving the organic EL elements 26, asillustrated in FIG. 4.

[0176] That is, the electric switches are composed of the scanningelectrode lines and the signal electrode lines which are electricallyconnected and, for example, the following: the first transistor(s)(which may be referred to as Tr1 hereinafter) 55, the secondtransistor(s) (which may be referred to as Tr2 hereinafter) andcondenser(s) 57, the number of each of which is one or more.

[0177] The first transistor 55 has a function of selecting one out ofluminescent pixels, and the second transistor 56 has a function ofdriving one of the organic EL elements.

[0178] An active layer 44 of each of the first transistor (Tr1) 55 andthe second transistor (Tr2) 56 can be represented by n⁺/i/n⁺. Asillustrated in FIG. 2, the regions n⁺ at the both side are composed ofsemiconductor regions 45 and 47 doped in an n type, and the region itherebetween is composed of a non-doped semiconductor region 46.

[0179] The semiconductor regions doped in an n type become a source 45and a drain 47, which constitute each of the transistors 55 and 56 asillustrated in FIG. 4, together with a gate disposed, across a gateoxide film, on the non-doped semiconductor region.

[0180] In the active layer 44, the semiconductor regions 45 and 47,which are doped in an n type, may be doped in a p type instead of the ntype so as to produce a structure of p⁺/i/p⁺.

[0181] The active layers 44 of the first transistor (Tr1) 55 and thesecond transistor (Tr2) 56 are preferably made of an inorganicsemiconductor such as polysilicone, or an organic semiconductor such asthiophene oligomer or poly(p-phenylenevinylene). Polysilicone is aparticularly preferable material since it has more sufficient stabilityagainst electric conduction than amorphous Si (α-Si).

[0182] (2) Driving Method

[0183] The following will describe the method of driving the organic ELelement by the TFT.

[0184] As illustrated in FIG. 4, the TFT comprises the first transistor(Tr1) 55 and the second transistor (Tr2) 56, and further constitutes theelectric switch.

[0185] Therefore, by inputting a scanning signal pulse and a signalpulse through an X-Y matrix to this electric switch to perform switchingaction, the organic EL element 26 connected to this electric switch canbe driven. As a result, the organic EL element 26 gives luminescence orthe luminescence is stopped so that image display can be performed.

[0186] That is, by a scanning pulse transmitted through the scanningelectrode lines (which may be referred to as gate lines) (Y_(j) toY_(j+n)) 50 and a signal pulse transmitted through the signal electrodelines (X_(i) to X_(i+n)) 51, a desired one out of the first transistors(Tr1) 55 is selected so that a given amount of charges is given into thecondenser 57 formed between common electrode lines (C_(i) to C_(i+n)) 52and the first transistor (Tr1) 55, as illustrated in FIG. 4.

[0187] In this way, the gate voltage of the corresponding secondtransistor (Tr2) 56 becomes a constant value so that the secondtransistor (Tr2) 56 turns on. In this ON-state, the gate voltage is helduntil the next gate pulse is transmitted. Therefore, electric current iscontinuously supplied to the lower electrode 22 of the organic ELelement 26 connected to the drain of the second transistor (Tr2) 56.

[0188] The organic EL element 26 is driven by the supplied electriccurrent. Thus, the driving voltage thereof is largely reduced and theluminescent efficiency thereof is improved. Moreover, the powerconsumption thereof can be reduced.

[0189] 6. Electrically Connecting Member

[0190] In the first embodiment, the electrically connecting member ispreferably made of a noncrystalline conductive oxide, for example,indium zinc oxide (IZO), as well as a metal material.

[0191] That is, due to the characteristics of the noncrystallineconductive oxide, such as moisture resistance and heat resistance, goodelectric connection can be obtained between the organic EL element andthe TFT.

[0192] And due to the excellent etching property that the noncrystallineconductive oxide has, the electrically connecting member superior inprecision can easily be formed.

[0193] Furthermore, the noncrystalline conductive oxide has acharacteristic of being superior in the capability of electricalconnection to the transparent electrode.

[0194] The noncrystalline conductive oxide preferably contains, as adopant or dopants for adjusting electric conductivity, for example, oneor a combination of two or more selected from Sn, Sb, Ga, Ge and so on.

[0195] [Second Embodiment]

[0196] As is roughly illustrated in FIG. 3, an organic EL display device70 of the second embodiment is an organic EL display device having thefollowing characteristics: the device 70 comprises, on a supportingsubstrate 10, third color changing medium 30 and 32, a transparent resinlayer (which may be referred to as a first transparent resin layer) 34,and an organic EL element 26 made of an organic luminescent medium 24sandwiched between a lower electrode 22 and an upper electrode 20; ELemission is taken out from the side of the lower electrode 22; and thedevice 70 satisfies the following expression (5)″ when the refractiveindex of the lower electrode 22 is represented by n5, those of the thirdcolor changing medium 30 and 32 are represented by n6(1) and n6(2),respectively, and that of the supporting substrate 10 is represented byn8.

[0197] As illustrated in FIG. 3, the organic EL display device 70 of thesecond embodiment preferably has the first transparent resin layer 34,that is, the layer corresponding to a flattening layer, an overcoatlayer, an inter-insulator or the like.

n5≦=n6(1)≦=n6(2)≦n8  (5)″

[0198] Referring to FIG. 3, the following will describe a characteristiccolor filter; a fluorescent medium for giving light having a colordifferent from that of EL emission; and so on in the second embodiment.

[0199] (1) Refractive Index

[0200] {circle over (1)} Expression (5)

[0201] By satisfying the expression (5) in the second embodiment, thereflectivity of EL emission on interfaces between the respective layerscan be lowered even if the third color changing medium is provided.Thus, an organic EL display device having a large luminescent quantitycan be provided.

[0202] For example, in the case that light is radiated from indium zincoxide (IZO, refractive index: 2.1) as the lower electrode and then thelight comes through the third color changing medium (refractive index:1.7) into the supporting substrate (refractive index: 1.5), the lightquantity incoming in the supporting substrate becomes a high value of98.6% of the light quantity (100%) outgoing from the IZO on theassumption that the light absorbance of the respective layers themselvesare 0%.

[0203] {circle over (2)} Expression (8)

[0204] As illustrated in FIG. 3, when the first transparent resin layer34 is arranged between the lower electrode 22 and the third colorchanging medium 30 and 32 and the refractive index of the firsttransparent resin layer 34 is represented by n7, it is preferred thatthe above-mentioned expression (5) is satisfied and the expression (8)is also satisfied.

n5≦n7≦n6≦n8  (8)

[0205] In the case that light is radiated from the lower electrode madeof, for example, indium zinc oxide (IZO, refractive index: 2.1) and thenthe light comes through the first transparent resin layer (refractiveindex: 1.7) and the third color changing medium(refractive index: 1.6)into the supporting substrate (refractive index: 1.5), by theabove-mentioned structure the light quantity incoming in the supportingsubstrate becomes a high value of 99% of the light quantity (100%)outgoing from the lower electrode on the assumption that the lightabsorbance of the respective layers themselves are 0%.

[0206] {circle over (3)} Expression (7)

[0207] When a transparent resin layer (which may be referred to as asecond transparent resin layer) is set between the third color changingmedium and the supporting substrate and the refractive index of thesecond transparent resin layer is represented by n7, it is preferred tosatisfy the above-mentioned expression (5) and further satisfy thefollowing expression (7):

n5≦n6≦n7≦n8  (7)

[0208] In the case that light is radiated from the lower electrode madeof, for example, indium zinc oxide (IZO, refractive index: 2.1) and thenthe light comes through the third color changing medium (refractiveindex: 1.6) and the second transparent resin layer (refractive index:1.6) into the supporting substrate (refractive index: 1.5), by theabove-mentioned structure the light quantity incoming in the supportingsubstrate becomes a high value of 98% of the light quantity (100%)outgoing from the lower electrode on the assumption that the lightabsorbance of the respective layers themselves are 0%.

[0209] {circle over (4)} Expression (11)

[0210] It is also preferred that the refractive index n5 of the lowerelectrode and the refractive index n6 of the third color changing mediumsatisfy the above-mentioned expression (5) and further satisfy thefollowing expression (11):

n6≦0.7×n5  (11)

[0211] In the case that light is radiated from the lower electrode madeof, for example, indium zinc oxide (IZO, refractive index: 2.1) and thenthe light comes through the third color changing medium(refractiveindex: 1.55) into the supporting substrate (refractive index: 1.5), bythe above-mentioned structure the light quantity incoming in thesupporting substrate becomes a high value of 98% of the light quantity(100%) outgoing from the lower electrode on the assumption that thelight absorbance of the respective layers themselves are 0%.

[0212] (2) Color Filter

[0213] {circle over (1)} Structure

[0214] The color filter is set in order to decompose or cut light raysto adjust color or improve contrast, and is comprising of a colorantlayer consisting only of a colorant or a layer wherein a colorant isdissolved or dispersed in a binder resin.

[0215] The structure of the color filter preferably comprises blue,green and red colorants. This is because combination of such a colorfilter with the organic EL element giving white luminescence makes itpossible to obtain the three primary colors of light, blue, green andred colors, and attain full color display.

[0216] The color filter is preferably patterned by printing orphotolithography as in the fluorescent medium.

[0217] {circle over (2)} Thickness of the Color Filter

[0218] The thickness of the color filter is not particularly limited ifthe thickness causes luminescence of the organic EL element to besufficiently received (absorbed) and does not block color changingfunction. For example, the thickness is preferably in the range of 10 nmto 1,000 μm, is more preferably in the range of 0.5 μm to 500 μm, and isstill more preferably in the range of 1 μm to 100 μm.

[0219] (3) Fluorescent Medium

[0220] {circle over (1)} Structure

[0221] The fluorescent medium in the organic EL display device has afunction of absorbing luminescence of the organic EL element to givefluorescence having longer wavelengths, and is comprising of layerarranged separately in plane. Each of the fluorescent medium layers ispreferably arranged correspondingly to the luminescent area of theorganic EL element, for example, the position of the portion where thelower electrode and the upper electrode cross each other. In the casethat the organic luminescent layer at the portion where the lowerelectrode and the upper electrode cross each other gives light, such astructure as above makes it possible that the respective fluorescentmedium layers receive the light so that luminescence rays havingdifferent colors (wavelengths) can be taken out. A structure wherein theorganic EL element emits blue light and further the light can be changedto green and red luminescence rays by the fluorescent medium isparticularly preferred since the three primary colors of light, blue,green and red colors, can be obtained even from the single organic ELelement so that full color display can be attained.

[0222] {circle over (2)} Constituent Material

[0223] The constituent material of the fluorescent medium is notparticularly limited and is made of, for example, a fluorescent dye anda resin, or only a fluorescent dye. The fluorescent dye and the resinmay be those in a solid state wherein the fluorescent dye is dissolvedor dispersed in a pigment resin and/or a binder resin.

[0224] Specific examples of the fluorescent dye will be described.Examples of the fluorescent dye for changing rays within the range fromnear-ultraviolet rays to violet luminescence rays in the organic ELelement to blue luminescence rays include stylbene colorants such as1,4-bis(2-methylstyryl)benzene (referred to as Bis-MBS hereinafter) andtrans-4,4′-diphenylstylbene (referred to as DPS hereinafter); andcoumarin dyes such as 7-hydroxy-4-methylcoumarin (referred to ascoumarin 4 hereinafter).

[0225] Examples of the fluorescent dye for changing blue, bluish greenor white luminescence rays in the organic EL element to greenluminescence rays include coumarin dye such as2,3,5,6-1H,4H-tetrahydro-8-trifluoromethylquinolidino(9,9a,1-gh)coumarin(referred to as coumarin 153 hereinafter),3-(2′-benzothiazolyl)-7-diethylaminocoumarin (referred to as coumarin 6)and 3-(2′-benzimidazolyl)-7-N,N-diethylaminocoumarin (referred to ascoumarin 7 hereinafter); Basic Yellow 51, which is a coumarin coloranttype dye; and naphthalimide dyes such as Solvent Yellow 11 and SolventYellow 116.

[0226] Examples of the fluorescent colorant for changing luminescencerays within blue to green luminescence rays, or white luminescence raysin the organic EL element to luminescence rays within orange to redluminescence rays include cyanine dyes such as4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (referredto as DCM hereinafter); pyridine dyes such as1-ethyl-2-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-pyridinium-perchlorate(referred to as pyridine 1); rhodamine dyes such as Rhodamine B andRhodamine 6G; and oxadine colorants.

[0227] Various dyes (direct dyes, acidic dyes, basic dyes, disperse dyesand so on) can be selected as fluorescent colorants if they havefluorescent property.

[0228] The fluorescent dye may be beforehand kneaded into the followingpigment resin to be made into a pigment: polymethacrylic acid ester,polyvinyl chloride, vinyl chloride vinyl acetate copolymer, alkyd resin,aromatic sulfonamide resin, urea resin, melamine resin, benzoguanamineresin or the like.

[0229] The binder resin is preferably a material having transparency(light transmittance to visible rays: 50% or more). Examples thereof aretransparent resins (polymers) such as polymethyl methacrylate,polyacrylate, polycarbonate, polyvinyl alcohol, polyvinyl pyrrolidone,hydroxyethylcellulose, and carboxymethylcellulose.

[0230] In order to arrange the fluorescent medium separately in plane, aphotosensitive resin to which photolithography can be applied may beselected. Examples thereof are photo-setting resist materials havingreactive vinyl groups, such as acrylic acid type, methacrylic acid type,polyvinyl cinnamate type and cyclic rubber type materials. In the casethat printing is used, a printing ink (medium) using a transparent resinis selected. For example, the following may be used: a monomer, anoligomer or a polymer of polyvinyl chloride resin, melamine resin,phenol resin, alkyd resin, epoxy resin, polyurethane resin, polyesterresin, maleic acid resin or polyamide resin; or a transparent resin suchas polymethyl methacrylate, polyacrylate, polycarbonate, polyvinylalcohol, polyvinyl pyrrolidone, hydroxyethylcellulose orcarboxymethylcellulose.

[0231] {circle over (3)} Refractive Index

[0232] For reference, the refractive indexes of materials constitutingpreferred fluorescent medium are as follows: vinyl chloride resin 1.54vinylidene chloride resin 1.60 vinyl acetate resin 1.45 polyethyleneresin 1.51 polystyrene resin 1.59 methyl methacrylate resin 1.49melamine resin 1.60

[0233] It is proved that these refractive indexes change by dissolvingor dispersing a dye for the fluorescent medium (or a colorant for thecolor filter). In the present invention, therefore, the refractive indexcan be adjusted by selecting a suitable material appropriately.

[0234] {circle over (4)} Forming Method

[0235] In the case that the fluorescent medium is made mainly of afluorescent dye, a film thereof is preferably formed by vacuumdeposition or sputtering through a mask for obtaining a desiredfluorescent medium pattern.

[0236] On the other hand, in the case that the fluorescent medium ismade of a fluorescent dye and a resin, the fluorescent medium ispreferably formed by mixing the fluorescent dye and the resin with anappropriate solvent or dispersing or dissolving the fluorescent dye andthe resin in the solvent to prepare a liquid material, making the liquidmaterial into a film by spin coating, roll coating, casting or the likeand subsequently patterning the film into a desired pattern byphotolithography or screen printing or the like.

[0237] {circle over (5)} Thickness

[0238] The thickness of the fluorescent medium is not particularlylimited if the thickness causes luminescence of the organic EL elementto be sufficiently received (absorbed) and does not block fluorescencegenerating function. For example, the thickness is preferably in therange of 10 nm to 1,000 μm, is more preferably in the range of 0.1 μm to500 μm, and is still more preferably in the range of 5 μm to 100 μm.

[0239] The reason for this is as follows. If the thickness of thefluorescent medium is less than 10 nm, the mechanical strength thereofmay drop or the lamination thereof may become difficult. On the otherhand, if the thickness of the fluorescent medium is over 1 mm, the lighttransmittance thereof drops remarkably so that the quantity of lightwhich can be taken out may drop or the organic EL display device may notbe easily made thin.

[0240] [Third Embodiment]

[0241] An organic EL display device of the third embodiment is anorganic EL display device having the following characteristics: thedevice comprises a color changing medium (which may be referred to as afourth color changing medium), a supporting substrate, a transparentresin layer (which may be referred to as a third transparent resinlayer), a lower electrode, an organic luminescent medium and an upperelectrode successively from the lower side thereof; EL emission is takenout through the fourth color changing medium from the side of the lowerelectrode; and the device satisfies the following expression (9) whenthe refractive index of the lower electrode is represented by n5, thatof the fourth color changing medium is represented by n9, and that ofthe supporting substrate is represented by n8:

n5≦n8≦n9  (9)

[0242] The following will describe a characteristic relationship betweenthe refractive indexes of the respective layers, and so on in the thirdembodiment. The fourth color changing medium can be made the same as thethird color changing medium described in the second embodiment.

[0243] (1) Expression (9)

[0244] By satisfying the expression (9) in the third embodiment, thereflectance of EL emission on interfaces between the respective layerscan be lowered even if the fourth color changing medium is arranged onthe side, opposite to the side on which the organic EL element isarranged, of the supporting substrate. Thus, an organic EL displaydevice having a large luminescent quantity can be provided.

[0245] For example, in the case that light is radiated from indium zincoxide (IZO, refractive index: 2.1) as the lower electrode and then thelight comes into the supporting substrate (refractive index: 1.5) andthen emits through the fourth color changing medium (refractive index:1.5) outside, the light quantity incoming in the fourth color changingmedium becomes a high value of 97.2% of the light quantity (100%)incoming from the lower electrode to the supporting substrate on theassumption that the light absorbance of the respective layers themselvesare 0

[0246] (2) Expression (10)

[0247] When the third transparent resin layer is arranged between thelower electrode and the supporting substrate and the refractive index ofthe third transparent resin layer is represented by n7, it is preferredto satisfy the above-mentioned expression (9) and further satisfy thefollowing expression (10):

n5≦n7≦n8≦n9  (10)

[0248] In the case that light is radiated from the lower electrode madeof, for example, indium zinc oxide (IZO, refractive index: 2.1) and thenthe light comes through the third transparent resin layer (refractiveindex: 1.7) into the supporting substrate (refractive index: 1.5) andsubsequently emits through the fourth color changing medium (refractiveindex: 1.5) outside, by the above-mentioned structure the light quantityincoming in the fourth color changing medium becomes a high value of98.5% of the light quantity (100%) incoming from the lower electrode tothe supporting substrate on the assumption that the light absorbance ofthe respective layers themselves are 0%.

[0249] (3) Expression (12)

[0250] It is also preferred that the refractive index n5 of the lowerelectrode and the refractive index n7 of the third transparent resinlayer arranged between the lower electrode and the supporting substratesatisfy the above-mentioned expression (10) and further satisfy thefollowing expression (12):

n7≦=0.7×n5  (12)

[0251] In the case that light is radiated from the lower electrode madeof, for example, indium zinc oxide (IZO, refractive index: 2.1) and thenthe light comes through the third transparent resin layer (refractiveindex: 1.55) into the supporting substrate (refractive index: 1.5), bythe above-mentioned structure the light quantity outgoing from thefourth color changing medium becomes a high value of 97.2% of the lightquantity (100%) incoming from the lower electrode into the supportingsubstrate on the assumption that the light absorbance of the respectivelayers themselves are 0%.

EXAMPLES Example 1

[0252] (1) Manufacture of Fluorescent Medium

[0253] A ball mill was used to mix homogeneously 100 g of an acrylictype photo-setting resist 259 PA having a fluorene skeleton (made byShin Nippon Steel chemical Co., Ltd. Solid content: 50% by weight, andpropylene glycol ether methyl ether acetate was used as a solvent) as aphoto-setting resin, 0.53 g of coumarin 6 as an organic fluorescent dye,1.5 g of Basic Violet 11, 1.5 g of Rhodamine 6G and 25 g of propyleneglycol methyl ether acetate as a solvent, so as to prepare a compositionfor a fluorescent medium (an ink for a fluorescent medium).

[0254] The resultant fluorescent medium composition was applied onto aglass substrate (Corning 7059) 25 mm in length, 75 mm in width and 1.1mm in thickness by spin coating, and then dried at 80° C. for 10minutes. Next, ultraviolet rays (wavelength: 365 nm) were radiatedthereon in such a manner that the quantity of light exposure would be1,500 mJ/cm², to form the fluorescent medium.

[0255] The refractive index of the fluorescent medium was measured, sothat it was 1.62. In the same way, the refractive index of the glasssubstrate was measured, so that it was 1.50.

[0256] In this way, a sealing member in which the fluorescent medium wasformed was manufactured.

[0257] (2) Manufacture of Organic EL Elements

[0258] A glass substrate (Corning 7059) 25 mm in length, 75 mm in widthand 1.1 mm in thickness was cleaned with isopropyl alcohol andultraviolet rays, and subsequently this substrate was fixed onto asubstrate holder inside a vacuum deposition machine (ULVAC, Co., Ltd.).

[0259] Next, a heating board made of molybdenum inside the vacuumevaporation machine was filled with4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MTDATA)and 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD) as holeinjection materials, 4,4′-bis(2,2-diphenylvinyl)biphenyl (DPVBi) as anorganic luminescent material, and tris(8-quinolynol)aluminum (Alq) as anelectron injection material, and further an Al/Li alloy (Li content bypercentage: 5% by weight) as a constituent material of lower electrodes(cathodes) was fitted to the heating board.

[0260] In this state, the evacuated pressure of the deposition machinewas reduced to 655×10⁻⁷ Pa and then the above-mentioned materials weredeposited by single vacuum drawing operation, without canceling thevacuum state on its way from the formation of the cathodes to theformation of a hole injection layer, in such a manner that the followingdeposition rates and film thicknesses would be attained.

[0261] MTDATA: deposition rate: 0.1 to 0.3 nm/sec., film thickness: 60nm,

[0262] NPD: deposition rate: 0.1 to 0.3 nm/sec., film thickness: 20 nm,

[0263] DPVBi: deposition rate: 0.1 to 0.3 nm/sec., film thickness: 50nm,

[0264] Alq: deposition rate: 0.1 to 0.3 nm/sec., film thickness: 20 nm,and

[0265] Al/Li alloy: deposition rate: 1.0 to 2.0 nm/sec., film thickness:150 nm.

[0266] Next, the substrate was moved to a sputtering machine, and thenIZO (refractive index: 2.1) for upper electrodes was sputtered into afilm to have a thickness of 200 nm. In this way, organic EL elementswere manufactured.

[0267] (3) Sealing Step

[0268] The organic EL elements obtained in the above-mentioned (2) wereput into a dry box which dry nitrogen was introduced. O-PET resin(refractive index: 1.63), which is a polyester resin having a fluoreneskeleton, was laminated on the luminescent faces (on the upperelectrodes) of the organic EL elements so as to form a film of thesealing medium.

[0269] Next, the glass substrate on which the fluorescent medium(refractive index: 1.62) obtained in the above-mentioned (1) was formed,that is, the sealing member (refractive index: 1.5) was laminated on thesealing medium.

[0270] In other words, the refractive index (n1: 2.1) of the upperelectrodes in the organic EL elements, the refractive index (n2: 1.63)of the sealing medium, the refractive index (n4: 1.62) of the firstcolor changing medium, and the refractive index (n3: 1.5) of the sealingmember were arranged in this way to satisfy the expression (2).

[0271] The peripheral portion thereof was treated with a cation-settingadhesive agent TB3102 (made by Three Bond Co., Ltd.), and then the agentwas set by light to make the resultant workpiece airtight. In this way,an organic EL display device of Example 1 was manufactured.

[0272] (4) Evaluation of the Organic EL Display Device

[0273] In Example 1, for evaluation of the first invention, a DC voltageof 12 V was applied through an active matrix circuit between the upperelectrodes (anodes, IZO) of the resultant organic EL display device andthe lower electrodes (cathode, Al/Li) thereof to give luminescence.

[0274] A chroma meter CS1000 (made by Minolta Co., Ltd.) was used tomeasure the luminescent brightness. As a result, a value of 62 cd/m² wasobtained. It was proved that the CIE chromaticity coordinates of theresultant red luminescence were as follows: X=0.62 and Y=0.34.

Comparative Example 1

[0275] In Comparative Example 1, a comparative example about the firstinvention was evaluated. Accordingly, in Comparative Example 1, anorganic EL display device was manufactured and evaluated in the samemanner as in Example 1 except that a silicone oil (refractive index:1.55) was filled and used instead of the O-PET resin used in Example 1.That is, an organic EL display device was formed in the manner that therefractive index (n1) of the upper electrodes, that (n2) of the sealingmedium, that (n4) of the color changing medium and that (n3) of thesealing member did not satisfy the relational expression (2).

[0276] Next, in the same way as in Example 1, the luminescent brightnessof the resultant organic EL display device was measured with chromameter CS1000. As a result, a value of 55 cd/m² was obtained as shown inTable 1. Red EL emission was obtained. It was proved that the CIEchromaticity coordinates thereof were as follows: X=0.62 and Y=0.34.

[0277] Thus, in Comparative Example 1 the same organic EL elements as inExample 1 were used, but it was proved that the luminescent brightnesswas reduced by about 11%.

[0278] It was demonstrated that when such silicone oil was used, theorganic EL elements were broken out after several minutes from themeasurement of the luminescent brightness so that EL emission could notbe obtained. TABLE 1 Side from which Luminescent luminescence brightnesswas taken out n1 n2 n4 n3 (cd/m²) Example 1 Upper 2.1 1.63 1.62 1.50 62electrode side Comparative Upper 2.1 1.55 1.62 1.50 55 Example 1electrode side Comparative Upper 2.1 1.30 1.62 1.50 50 Example 2electrode side Comparative Upper 2.1 1.00 1.62 1.50 29 Example 3electrode side

Comparative Example 2

[0279] In Comparative Example 2, a comparative example about the firstinvention was evaluated. Accordingly, in Comparative Example 2, anorganic EL display device was manufactured and evaluated in the samemanner as in Example 1 except that fluorinated hydrocarbon liquidFlorinate (made by Sumitomo 3M Limited, refractive index: 1.3) wasfilled and used instead of the O-PET resin in Example 1. That is, anorganic EL display device was formed in the manner that the respectiverefractive indexes did not satisfy the expression (2).

[0280] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the upper electrodes (anodes, IZO) of the resultantorganic EL display device and the lower electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0281] As a result, a luminescent brightness value of 50 cd/m² wasobtained. It was proved that the CIE chromaticity coordinates of theresultant red luminescence were as follows: X=0.62 and Y=0.34.

[0282] Thus, in Comparative Example 2 the same organic EL elements as inExample 1 were used, but it was proved that the luminescent brightnesswas reduced by about 19%.

Comparative Example 3

[0283] In Comparative Example 3, a comparative example about the firstinvention was evaluated. Accordingly, in Comparative Example 3, anorganic EL display device was manufactured and evaluated in the samemanner as in Example 1 except that dry nitrogen (refractive index: 1.0)was filled and used instead of the O-PET resin in Example 1. That is, anorganic EL display device was formed in the manner that the respectiverefractive indexes did not satisfy the relational expression (2).

[0284] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the upper electrodes (anodes, IZO) of the resultantorganic EL display device and the lower electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0285] As a result, a luminescent brightness value of 29 cd/m² wasobtained. It was proved that the CIE chromaticity coordinates of theresultant red luminescence were as follows: X=0.62 and Y=0.34.

[0286] Thus, in Comparative Example 3 the same organic EL elements as inExample 1 were used, but it was proved that the luminescent brightnesswas reduced by about 50%.

Example 2

[0287] In Example 2, the second invention was evaluated. Accordingly, inExample 2 an organic EL display device wherein a first transparent resinlayer 34 was arranged between a lower electrode 22 and second changingmedium 30 and 32 and further EL emission was taken out from the lowerelectrode side, as illustrated in FIG. 3, was manufactured andevaluated.

[0288] That is, ITO (refractive index: 1.8) was used as the lowerelectrode (transparent electrode), the O-PET resin (refractive index:1.63) used in Example 1 was used as the first transparent resin layer,and the second changing medium comprising of the fluorescent medium 30and the color filter 32 (refractive index of the combination of the two:1.62) were arranged thereon. Furthermore, a glass substrate (refractiveindex: 1.50) was used as a supporting substrate 10. In this way, anorganic EL display device was formed in the manner that the values ofthe respective refractive indexes satisfy the expression (8).

[0289] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the lower electrodes (anodes, ITO) of the resultantorganic EL display device and the upper electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0290] As a result, a high value of 75 cd/m² was obtained. It was provedthat the CIE chromaticity coordinates of the resultant red luminescencewere as follows: X=0.62 and Y=0.34. TABLE 2 Side from which Luminescentluminescence brightness was taken out n5 n7 n6 n8 (cd/m²) Example 2Lower 1.8 1.63 1.62 1.50 75 electrode side Comparative Lower 1.8 1.501.62 1.50 60 Example 4 electrode side

Comparative Example 4

[0291] In Comparative Example 4, a comparative example about the secondinvention was evaluated. Accordingly, in Comparative Example 4 anorganic EL display device was manufactured and evaluated in the samemanner as in Example 2 except that a SiOx sputtering film (refractiveindex: 1.50) was used instead of the O-PET resin in Example 2. That is,an organic EL display device was manufactured in the manner that therefractive index values did not satisfy the expression (8).

[0292] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the lower electrodes (anodes, ITO) of the resultantorganic EL display device and the upper electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0293] As a result, a luminescent brightness value of 60 cd/m² wasobtained. It was proved that the CIE chromaticity coordinates of theresultant red luminescence were as follows: X=0.62 and Y=0.34.

[0294] Thus, in Comparative Example 4 the same organic EL elements as inExample 2 were used, but it was proved that the luminescent brightnesswas reduced by about 20%.

Example 3

[0295] In Example 3, another embodiment of the second invention wasevaluated. Accordingly, in Example 3 an organic EL display device wasmanufactured and evaluated in the same manner as in Example 2 exceptthat no color changing medium was arranged. That is, an organic ELdisplay device was formed in the manner that the refractive index (n5)of the lower electrodes, that (n7) of the transparent resin layer andthat (n8) of the supporting substrate satisfied the expression (6).

[0296] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the lower electrodes (anodes, ITO) of the resultantorganic EL display device and the upper electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0297] As a result, a high luminescent brightness value of 200 cd/m2 wasobtained. It was proved that the CIE chromaticity coordinates of theresultant blue luminescence were as follows: X=0.14 and Y=0.20. TABLE 3Side from which Luminescent luminescence brightness was taken out n5 n7n8 (cd/m²) Example 3 Lower 1.8 1.63 1.50 200 electrode side ComparativeLower 1.8 1.43 1.50 150 Example 5 electrode side

Comparative Example 5

[0298] In Comparative Example 5, a comparative example about the secondinvention was evaluated. Accordingly, in Comparative Example 5, anorganic EL display device was manufactured and evaluated in the samemanner as in Example 3 except that polytrifluoroethylene (refractiveindex: 1.43) was used instead of the O-PET resin as the transparentresin layer in Example 3. That is, an organic EL display device wasformed in the manner that refractive index (n5) of the lower electrodes,that (n7) of polytrifluoroethylene and that (n8) of the supportingsubstrate did not satisfy the expression (6).

[0299] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the lower electrodes (anodes, ITO) of the resultantorganic EL display device and the upper electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0300] As a result, a value of 150 cd/m² was obtained. It was provedthat the CIE chromaticity coordinates of the resultant blue luminescencewere as follows: X=0.14 and Y=0.20.

[0301] Thus, in Comparative Example 5 the same organic EL elements as inExample 3 were used, but it was proved that the luminescent brightnesswas reduced by about 25%.

Example 4

[0302] In Example 4, the third invention was evaluated. Accordingly, inExample 4 an organic EL display device was manufactured and evaluated inthe same way as in Example 3 except that a fourth color changing mediumwas arranged on the side, opposite to the side on which the transparentresin layer was arranged, of the supporting substrate, PMMA (polymethylmethacrylate resin) was used as matrix material to provide therefractive index of the fourth color changing medium to 1.5, and furtherthe lower electrodes (anodes) were composed of IZO.

[0303] That is, an organic EL display device was formed in the mannerthat the refractive index (n5) of the lower electrodes, that (n7) of thetransparent resin layer, that (n8) of the supporting substrate and that(n9) of the fourth color changing medium satisfied the expression (10).

[0304] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the lower electrodes (anodes, IZO) of the resultantorganic EL display device and the upper electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0305] As a result, a luminescent brightness value of 57 cd/m² wasobtained. It was proved that the CIE chromaticity coordinates of theresultant red luminescence were as follows: X=0.62 and Y=0.34. TABLE 4Side from which Luminescent luminescence brightness was taken out n5 n7n8 n9 (cd/m²) Example 4 Lower 2.1 1.63 1.50 1.50 57 electrode sideComparative Lower 2.1 1.43 1.50 1.50 45 Example 6 electrode side

Comparative Example 6

[0306] In Comparative Example 6, a comparative example about the thirdinvention was evaluated. Accordingly, in Comparative Example 6 anorganic EL display device was manufactured and evaluated in the samemanner as in Example 4 except that polytrifluoroethylene (refractiveindex: 1.43) was used instead of the transparent resin layer in Example4. That is, an organic EL display device was formed in the manner thatrefractive index (n5) of the lower electrodes, that (n7) ofpolytrifluoroethylene and that (n8) of the supporting substrate did notsatisfy the expression (10).

[0307] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the lower electrodes (anodes, IZO) of the resultantorganic EL display device and the upper electrodes (cathodes, Al/Li)thereof. The chroma meter CS1000 was used to measure the luminescentbrightness.

[0308] As a result, a luminescent brightness value of 45 cd/m² wasobtained. It was proved that the CIE chromaticity coordinates of theresultant red luminescence were as follows: X=0.62 and Y=0.34.

[0309] Thus, in Comparative Example 6 the same organic EL elements as inExample 4 were used, but it was proved that the luminescent brightnesswas reduced by about 21%.

Example 5

[0310] In Example 5, the first invention was evaluated. That is, anorganic EL display device was manufactured under the same conditions asin Example 1 except that a sealing member having no fluorescent mediumwas used.

[0311] Namely, an organic EL display device was formed in the mannerthat the refractive index (n1: 2.1) of the upper electrodes in theorganic EL element, that (n2: O -PET resin 1.63) of the sealing medium,and that (n3: 1.5) of the sealing member satisfied the expression (1).

[0312] Next, a DC voltage of 12 V was applied through an active matrixcircuit between the upper electrodes (anodes, IZO) of the resultantorganic EL display device and the lower electrodes (cathodes, Al/Li)thereof to give luminescence.

[0313] The chroma meter CS1000 (made by Minolta Co., Ltd.) was used tomeasure the luminescent brightness. As a result, a value of 200 cd/m²was obtained. It was proved that the CIE chromaticity coordinates of theresultant blue luminescence were as follows: X=0.15 and Y=0.16.

Comparative Example 7

[0314] In Comparative Example 7, a comparative example about the firstinvention was evaluated. Accordingly, in Comparative Example 7 anorganic EL display device was manufactured and evaluated in the samemanner as in Example 5 except that nitrogen gas (refractive index: 1.00)was used as a sealing medium instead of the O-PET resin used in Example5. That is, an organic EL display device was formed in the manner thatrefractive index (n1) of the upper electrodes, that (n2) of the sealingmedium and that (n3) of the sealing member did not satisfy theexpression (1).

[0315] Next, the chroma meter CS1000 was used to measure the luminescentbrightness of the resultant organic EL display device in the same manneras in Example 5. As a result, a value of 160 cd/m² was obtained, asshown in Table 5. Blue luminescence was obtained. It was proved that theCIE chromaticity coordinates thereof were as follows: X=0.15 and Y=0.16.

[0316] Thus, in Comparative Example 7 the same organic EL elements as inExample 5 were used, but it was proved that the luminescent brightnesswas reduced by about 20%.

[0317] It was demonstrated that when nitrogen gas was used as thesealing medium in this way, the luminescent brightness droppedremarkably since the expression (1) was not satisfied. TABLE 5 Side fromwhich Luminescent luminescence was brightness taken out n1 n2 n3 (cd/m²)Example 5 Upper 2.1 1.63 1.50 200 electrode side Comparative Upper 2.11.00 1.50 160 Example 7 electrode side

INDUSTRIAL APPLICABILITY

[0318] According to the first invention (organic EL display device) ofthe present invention, the relationship between the refractive index ofthe sealing member and those of the electrode and so on is considered.According to the second invention (organic EL display device), therelationship between the refractive indexes of the color changing mediumand the transparent resin and those of the electrode and so on isconsidered. According to the third invention (organic EL displaydevice), the relationship between the refractive index of the colorchanging medium arranged outside the supporting substrate and those ofthe electrode and so on is considered. In these ways, reflection on therespective interfaces is suppressed and the quantity of EL emissionwhich can be taken out can be made large even if silicone oil or thelike is not used as the sealing medium.

1. An organic electroluminescence display device comprising; asupporting substrate; an organic electroluminescence element comprisingan organic luminescent medium sandwiched between a lower electrode andan upper electrode on the supporting substrate; a sealing medium; and asealing member; electroluminescence emission being taken out from theupper electrode; wherein a following expression (1) is satisfiedn1≦n2≦n3  (1) wherein n1 represents a refractive index of the upperelectrode, n2 represents a refractive index of the sealing medium, andn3 represents a refractive index of the sealing member.
 2. The organicelectroluminescence display device according to claim 1, wherein thedevice further comprises a color changing medium between the sealingmedium and the sealing member; and a following expression (2) issatisfied n1≦n2≦n4≦n3  (2) wherein n4 represents a refractive index ofthe color changing medium.
 3. The organic electroluminescence displaydevice according to claim 1, wherein the device further comprises acolor changing medium on a surface of the sealing member, the surfaceopposite to a surface on which the sealing medium is arranged; and afollowing expression (3) is satisfied n1≦n2≦n3≦n4′  (3) wherein n4′represents a refractive index of the color changing medium.
 4. Theorganic electroluminescence display device according to any one ofclaims 1 to 3, wherein the refractive indexes n1 and n2 satisfy afollowing expression (4). n2≦=0.7×n1  (4)
 5. The organicelectroluminescence display device according to any one of claims 1 to4, wherein the refractive index of the sealing medium is 1.56 or more.6. The organic electroluminescence display device according to any oneof claims 1 to 5, wherein the sealing medium comprises a transparentresin and/or a sealing liquid.
 7. The organic electroluminescencedisplay device according to any one of claims 1 to 6, wherein thesealing medium comprises a transparent inorganic material.
 8. Theorganic electroluminescence display device according to any one ofclaims 1 to 7, wherein the upper electrode is made mainly of an indiumzinc oxide.
 9. An organic electroluminescence display device comprising;a supporting substrate; and an organic electroluminescence elementcomprising an organic luminescent medium sandwiched between a lowerelectrode and an upper electrode, on the supporting substrate; a colorchanging medium and/or a transparent resin layer being arranged betweenthe supporting substrate and the lower electrode; electroluminescenceemission being taken out from the lower electrode; wherein any one offollowing expressions (5) to (8) is satisfied n5≦n6≦n8  (5)n5≦n7≦n8  (6) n5≦n6≦n7≦n8  (7) n5≦n7≦n6≦n8  (8) wherein n5 represents arefractive index of the lower electrode, n6 represents a refractiveindex of the color changing medium, n7 represents a refractive index ofthe transparent resin layer, and n8 represents a refractive index of thesupporting substrate.
 10. An organic electroluminescence display devicecomprising; a supporting substrate; and an organic electroluminescenceelement comprising an organic luminescent medium sandwiched between alower electrode and an upper electrode, on the supporting substrate; acolor changing medium being arranged on a surface of the supportingsubstrate, the surface opposite to a surface on which the lowerelectrode is arranged; electroluminescence emission being taken out fromthe side of the lower electrode; wherein a following expression (9) issatisfied n5≦n8≦n9  (9) wherein n5 represents a refractive index of thelower electrode, n8 represents a refractive index of the supportingsubstrate, and n9 represents a refractive index of the color changingmedium.
 11. The organic electroluminescence display device according toclaim 10, wherein a transparent resin layer is arranged between thelower electrode and the supporting substrate, and a following expression(10) is satisfied; n5≦n7≦n8≦n9  (10) wherein n7 represents a refractiveindex of the transparent resin layer.
 12. The organicelectroluminescence display device according to any one of claims 9 to11, wherein the refractive index n5, and the refractive index n6 or n7satisfy the following expression (11) or (12). n6≦0.7×n5  (11) n 7≦0.7×n5  (12)
 13. The organic electroluminescence display device according toany one of claims 1 to 12, wherein a thin film transistor for drivingthe organic electroluminescence element is arranged on the supportingsubstrate.